Treatment of nitrocellulose dope



.10; low degree of inflammability as compared with .20, treat a solution of nitrocellulose, for example a Patented Oct. 17, 1933 I l t V I v UNITED3-STATES P EN om n "No Drawing. Application November 24, 1931 Y Serial No. 577,166 9 V Thepr'esent invention relates. toftre'ating nitro- At this stage a softener or plasticizing'agent cellulose dope (i. e; viscous solutions of nitrocelcan be added, to the amount of, one-half ounce lulose in suitable volatile organic solvents) such p eal no the Washed m aiw h W m as is used for coatingrairplanes; balloons and to l fi f DQ1 ofthe Wei h h similar fabrics, and the objectisgtoimprove the s undef m A5 u t l c ng 60,

dope, and to improve the film'of material left g n Q s Oil,- a rir PhQSPhate r when the dope is applied to the said fabric and mentioned? other similarly ti q n r e dried, particularly: rendering the dried coating be 1 lP QYd-, t f r I Substantially n i fl bl or at least of a The cellulosic material and softener are worked together, for example by a stirring and kneading action, during which operation a further amount r of the water in the mass may separate out mechanically, which can be discarded. Then, without drying, the mixture of cellulosic compound and castor oil (or other softener) is added to the proportion of plasticizmg agents and the another three volumes of the original dope. To cific character of the solvents employed, are all m clear the matter of proportlonsi assummg more or less Variab1e one gallon of the original dope was used in apar- In accordance with the present invention 1 ticular case, the resulting cellulosic material and softener would be then added to three gallons of the untreated dope. This amount will readily dissolve in the dope, and thinners such as alcohols or acetates, or other diluents, can then be added to obtain the desired consistency.

It will of course be understood that the invention is in no sense restricted to dope to be applied to fabrics, but can be applied in a similar manner to various other nitrocellulose solutions. The

final mixture of cellulosic compound and softener can be dissolvedin a dope or in any other nitrocellulose solvent.

In some cases it is advisable to dissolve the cellulosic material from one volume of dope, in less than three volumes of untreated dope, for

' a color and apparently contains ad; example two Volumes 01 two and one-half v01- dition to the cellulosic compound, zinc compounds umes- In some cases this material Could be and some acid. This stringy mass is thenwashed ed to r than three Volumes. of 5 19 one or more times with a solution of magnesium I c1aim3 sulfate, for example a solution containing about A Process which compriSes treating ,40 6to 10% of Epsom salts (crystallized magnesium tion of nitrocellulose with an aqueousacid solusulfate). This turns the stringy mass to a praction of a zinc salt to produce precipitation of the tically white condition, and washes out the renitrocellulose, then drawing off the acid liquid, maining free hydrochloric, acid. One or more washing the residue with an aqueous solution of washings with the magnesium sulfate will be sufa magnesium salt, and finally washing same with 45 ficient, and it is advisable to test at this stage water; adding aplasticizer to the'wet residue and to see that the cotton-like stringy mass is subworking the same together with further separastantially acid free. This can be tested with littion of water, and dissolving such product in a mus P p y adding a little Sodium bicar liquid containing volatile solvents bonate which would cause considerable efierves- 2. A'process asin claim 1, in which the acid 50 cence if free acid is still present. The mass is aqueous solution of zinc salt is a substantially then washed with water one or more times, and saturated solution of zinc chloride in hydrois allowed to stand and drain for the excess water chloric acid, and in which the aqueous solution to drain away. It is not necessary at this stage of a magnesium salt is a 6 to 10% solution of to dry the material, but most of the water can Epsom salt in water. l i

.be separated out by gentle pressure. 7 3. A process which comprises treating a nitro- 119 the highly inflammable nitrocellulose.

It is of course understood that the dopes now on the market, made by difierent manufacturers have different chemical compositions, that is to 15 say the proportion of nitrocellulose therein and nitrocellulose dope which may be any one of those now on the market. To the solution of nitrocellulose, for example nitrocellulose dope, I add an acid solution of zinc salt, preferably zinc chlo- 25 ride dissolved in commercial strong hydrochloric acid (1.2 gravity) to substantial saturation. I prefer to use about 2 volumes of this zinc salt solution to 1' volume of the nitrocellulose dope. These two materials are well mixed together, 30' which produces coagulation of the nitrocellulose, and the liquids are thoroughly mixed, while being poured together. The cellulosic compound is thereby converted into the insoluble condition,

as a more or less stringy mass. This will be of cellulose dope with more than its own volume ot a substantially saturated solution of zinc chloride in concentrated aqueous hydrochloric acid, to cause a coagulation of the nitrocellulose, washing the latter with a dilute aqueous solution of Epsom salt, thereafter washing same with water, and dissolving the product in a pyroxylin solvent.

4. A process which comprises treating a nitrocellulose dope with more than its own volume of a substantially saturated solution of zinc chloride in concentrated aqueous hydrochloric acid, to cause a coagulation of the nitrocellulose, washing the latter with a dilute aqueous solution of Epsom salt, thereafter washing same with water, mixing the residue with a small percentage of a plasticizing agent, and dissolving the mixture in a'liquid containing a nitrocellulose solvent. I

5. A process which comprises treating a nitrocellulose dope with more than its own volume of a substantially saturated solution of zinc chloride in concentrated aqueous hydrochloric acid, to cause a coagulation of the nitrocellulose, Washing the latter with a dilute aqueous solution of Epsom salt, thereafter washing same with water, and thereafter dissolving the residue in a nitrocellulose done.

6. A process which comprises treating a nitrocellulose dope with more than its own volume of a substantially saturated solution of zinc chloride in concentrated aqueous hydrochloric acid,

per cent of a liquid plasticizing agent and thereafter dissolving the mixture in a nitrocellulose dope, to produce a dope which, upon being applied and dried, is of reduced inflammability.

7. A process which comprises treating a nitrocellulose dope. with more than its own volume of a substantially saturated solution of zinc chloride in concentrated aqueous hydrochloric acid, to cause a. coagulation of the nitrocellulose, washing the latter with a dilute aqueous solution of Epsom salt, thereafter washing same with water, mixing the residue with about one-half per cent of a liquid plasticizing agent and thereafter dissolving the mixture in a nitrocellulose dope and adding more pyroxylin solvent as a thinner, to produce a dope which, upon being applied and dried, is of reduced inflammability.

8. Nitrocellulose dope having the properties of the product of claim 7.

IiINTON c. AMBERSON. 

